Kindly explain this command

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moonman 2011-9-22

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final_song = cellfun(@plus, alto, treb, 'Uniform', 0);

Kindly explain this command. Basically i want to add alto and treb and they are being added. what does uniform and 0 mean in this command

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Answer 1

Grzegorz Knor 2011-9-22

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Option Uniform or UniformOutput set to 0 (or false) means, that output from function will be stored in cell array. It is necessary when function (in your case plus) returns non scalar values. If you set the UniformOutput value to 1 ( or true), your function must return scalar values and the output will be concatenated into an array.

Look at examples:

a = {rand(1),rand(2),rand(3),rand(4)}
b = {rand(1),rand(2),rand(3),rand(4)}
cellfun(@plus,a,b,'UniformOutput', false)
a = {rand(1),rand(1),rand(1),rand(1)}
b = {rand(1),rand(1),rand(1),rand(1)}
cellfun(@plus,a,b,'UniformOutput', false)
a = {rand(1),rand(1),rand(1),rand(1)}
b = {rand(1),rand(1),rand(1),rand(1)}
cellfun(@plus,a,b,'UniformOutput', true)

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Grzegorz Knor 2011-9-22

So you have the answer. The sum of two matrices (vectors) is a matrix (vector) and not a scalar.

moonman 2011-9-22

Thanks a lot

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Answer 2

Jan 2011-9-22

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Have you read "help cellfun" and "<http://www.mathworks.com/help/techdoc/ref/cellfun.html doc cellfun>" already?

There you find the information, that 'Uniform' is an abbreviation for 'UniformOutput' - sometimes neato users write 'Uni' only. And the description is:

 a logical value indicating whether or not the output(s) of FUN can be
 returned without encapsulation in a cell array

Actually the parameter should be of type LOGICAL, but MATLAB converts the 0 kindly to FALSE, as a 1 is converted to TRUE. Try this:

f = cellfun(@plus, {1}, {2}, 'Uniform', 0);
disp(f);
disp(class(f));
f = cellfun(@plus, {1}, {2}, 'Uniform', 1);
disp(f);
disp(class(f));
f = cellfun(@plus, {1}, {[2, 3]}, 'Uniform', 0);
disp(f);
disp(class(f));
% But this fails, because the output cannot be written to a vector,
% because the elements have different sizes:
f = cellfun(@plus, {1}, {[2, 3]}, 'Uniform', 1);